Re: Confused about PAP object layout

Disclaimer: I am not an expert. But I happened to have been looking at this code just yesterday, so I’ll try to answer to check my understanding. :) Fundamentally, a PAP is not fully-saturated, so the number of arguments in its payload may be smaller than the information contained in the function’s bitmap. scavenge_large_bitmap calls walk_large_bitmap, which uses the bitmap as a “ruler” to guide the traversal, lining up each element in the payload to information in the bitmap. But the traversal only actually walks a payload of the specified size, so if there’s less information in the payload than there is information in the bitmap, the traversal will just terminate early.

On Feb 14, 2020, at 09:30, Ömer Sinan Ağacan wrote:

Right, I think that's the problem. We then pass the same "size" to scavenge_large_bitmap as the size of the bitmap. So we assume size of the bitmap is pap->n_args.

So the call stack is

- scavenge_PAP, calls scavenge_PAP_payload with pap->n_args as "size" - scavenge_PAP_payload, calls scavenge_large_bitmap with "size" (== pap->n_args) as the bitmap's size

Is this expected?

Ömer